On Thu, 2009-01-22 at 11:32 -0600, Jeremy Shaw wrote: > Hello, > > Just some minor suggestions and comments: > > The description might read better as two sentences: > > A class for monoids with various general-purpose instances. Monoids > are types with an associative binary operation that has an > identity. > > One thing that I think is a bit unclear from that description is the > fact that it does not matter *what* the binary operation does, as long > as the laws are followed. That is the whole point of the monoid class > -- you use it when you only care about the laws, not the specific > operation... > > For the laws, it would be nice to label each rule, something like > > * mappend mempty x = x -- Left Identity > * mappend x empty = x -- Right Identity > * mappend x (mappend y z) = mappend (mappend x y) z -- Associative
> * mconcat = foldr mappend mempty -- Not sure what to > call this. Perhaps it an axiom? This is just a definition, both actually and nominally. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
